Music: Practice & Theory Stack Exchange is a question and answer site for musicians, students, and enthusiasts. It only takes a minute to sign up.
Sign up to join this community
This song goes Fm9 - Bb13 - Bbm9 - C7b9(#5) As far as I can tell this is a 1-4-5 in F minor... but what about the Bb13 ? Note that this vamps repeats over and over ...the song is pretty fast ..maybe 2 seconds on each chord maximum... Should it be considered just a passing chord ? What is the theory behind ? Thanks!
Wow , this generated more discussion than I thought ....here is the song :
...I`m analysing all the answers you folks kindly shared... Thank you !!For starters, this is definitely an F minor progression. Do not interpret this as Eb in the absence of any Eb chords.
IV7 while in a minor key is a common use of modal interchange. It's borrowed from the dorian mode. It's common because it's a very strong suggestion of dorian (since it contains the nat6) and it is easy to return to the original key (by flatting the sixth again). This also creates a chromatic voice leading starting from the b7th of the scale and descending to the 5th if you then go to V7 or the root (in this case, Eb-D-Db-C).
By extension, it is useful to interpret the BbMi9 as the restatement of the key. You often see Db7#11 in this position, and in that sense it is somewhat unusual to see the ninth (C), but there is no need to overthink this. BbMi9 represents the subdominant of the key and the progression is a typical minor i-iv-V with a quick trip to the parallel dorian.
It's a kind of modal borrowing--in the context of F minor, Bb13 is arguably borrowed from the tonic major (F major). Think of it as IV13.
There is a good way to interpret the progression so that the B♭13 isn't out of place/being borrowed from a different mode. Think of the first two measures as being in F Dorian and the last two measures as being a iiø-V7alt in F min. The advantage of this approach is that there is more cohesion/continuity between the Fmin and B♭13 chords.
The B♭min chord is serving a subdominant function: it preps the V7 chord, C7alt. In this way, it is interchangeable with Gø7. In fact, if we replaced B♭m9 with B♭m6 (which wouldn't change the function of the B♭m chord), then now the B♭m6 chord would be voiced B♭-D♭-F-G, which is also the exact spelling of a Gø7 chord. In general, ii-V-i progressions and iv-V-i progressions are both commonly found in music, and are often interchangeable.
Just as we could treat the B♭m9 chord as B♭m6, the Fm chord can be interpreted through many different scales (F melodic minor, F Dorian minor, F Aeolian minor, etc.). If you want the first two measures to be continuous, then you would choose F Dorian minor for measure 1, since F Dorian contains the D♮ from the B♭13 chord. In effect, you'd be treating the Fmin9 chord as Fmin6 (or more technically Fmin6/9). This interpretation/approach would create good cohesion in the first two measures, since both chords would now contain a D♮. When improvising, for example, an Fmin6 pentatonic scale would sound great (F-G-A♭-C-D) and would be seamless when passing from one chord to the next.
So ultimately, the way to think about this progression is as a i-IV7-iiø7-V7alt, with the first two measures using F Dorian and the last two measures being a turnaround:
| Fm6/9 | B♭13 | Gø7 | C7alt |
Other interpretations are possible. For example, you could interpret the Fm9 chord as implying F Aeolian (i.e., F natural minor). Doing this would cause the B♭7 chord to stick out more, because it'll be the only chord in the four measures that contains a D♮. One downside of using F Aeolian is that the D♭ will be an avoid note over the Fm9 chord, whereas the D♮ wouldn't. If you use F Dorian, then now the D♭ from C7alt can resolve down a half step to C or up a half step to D♮.
So if you're trying to make the B♭7 chord be more cohesive with the other chords, I recommend the approach I've outlined above. (Of course, if you're comping/playing chords behind a soloist, you want to listen to what the soloist is playing and let that dictate your choices too. If the soloist is playing a D♭ over the Fm9 chord, then avoid a D♮.)
Seems it might be using F Dorian, Which sounds similar to F minor, but the IV chord becomes Bb major. The fact that it's a 13th chord, with at least a 6th and a m7th doesn't really make a lot of difference. Then maybe it reverts to Fm proper, before going to V on C. The Bb major could be called a borrowed chord from the parallel key of F major, if you want a bit of alternate theory.
Having listened to 'this song', it might make matters different...
Try hearing it as ii7, V7, v7, VI7 in Eb. The fact that it isn't wrapped up with Fm7, Bb7, Eb doesn't matter.
